This invention relates to center pivot irrigation systems, and in particular to a control device therefor.
Pivot type sprinklers are used widely in semi-arid regions for irrigation of large agricultural areas. Such sprinklers include an elongate water pipe having one end pivotally mounted at a source of water, such as a well, and are supported above the ground by a plurality of spaced apart vehicles. Each of the vehicles includes a motor for moving the water pipe over the ground.
These center pivot sprinkler systems require a substantial amount of power during operation due to the extreme weight of the water in the line, as well as irregularities in the field over which the sprinkler vehicles traverse. Some pivot sprinkler systems are water driven, and use the water pressure in the irrigation pipe to operate the vehicle motors, which are typically cylinders. The pressure required to properly operate the cylinders is very high, and consequently, high pressure water must be supplied along the entire length of the water pipe, thereby requiring high pressure pumps, water lines, and other equipment, as well as requiring substantial energy consumption.
Pivot sprinkler systems are alternatively powered by a separate hydraulic drive, such that the water pressure in the water line may be reduced substantially without adversely effecting the power of the support vehicles. Again, the operating pressure required to properly activate the hydraulic cylinders is quite high, and the hydraulic drive units are therefor susceptible to overheating which breaks down the hydraulic fluid, reduces operating efficiency, and often causes damages to the sprinkler equipment, such as the pumps, seals, manifolds, and the like. Heretofore, the drive units for the center pivots sprinkler systems have not proven to be both efficient and dependable.
Another cause of sprinkler malfunction relates to the extreme misalignment of the sprinkler vehicles. A variety of devices are available for maintaining the sprinkler vehicles in alignment as they are driven. However, such devices are typically quite complex and expensive, and when used in combination with the hydraulic drive type of unit, permit the hydraulic cylinders to operate with lost motion or to short stroke when the vehicle wheels encounter high resistance, such as large rocks, heavy mud, or the like. This lost motion can cause severe misalignment of the sprinkler vehicles, and activate an automatic misalignment shut-off, or cause substantial damage to the sprinkler system.
Repair to the sprinkler system as a result of the damage caused by any one of the above noted problems is not only time consuming and expensive, but may result in complete crop failure if the system is not brought to an operative condition within a relatively short period of time.